Thin Dielectrics Research Articles

Heat and mass transfer by generalized complex variables during heat treatment and drying of thermal insulation materials

The results of processing experimental data on heat treatment in drying processes of thin thermal insulation materials are presented. As a result of processing the experimental data by generalized complex variables, formulas for determining the heat flux density, average integral temperatures, the intensity of moisture evaporation, and the duration of the heat treatment process of materials were obtained. Based on the elements of the thermal regular regime theory, formulas for determining the rate of heating of the wet body and the rate of loss of moisture content have been established by processing experimental data using the least squares method. The conditions of the drying process in the regular mode are considered. Processing experimental data with generalized complex variables allows you to move from one coordinate system to another, from one variable to another, without performing additional time-consuming experiments. Based on the equation of drying kinetics and the generalized drying curve, the relationship between the dimensionless heat flux and the relative drying rate is given. For the single-zone method of calculating the drying rate curve, an approximate relationship for determining the relative drying rate is given. The relationship between material surface temperature and the relative drying rate in the heat treatment processes of ceramic tiles, asbestos sheets, wool felts was established. All of the above formulas were used to check the reliability of the obtained dependencies, as well as to compare the calculated values of the main parameters of the drying kinetics with the experiment.

Control of Néel Vector with Spin-Orbit Torques in an Antiferromagnetic Insulator with Tilted Easy Plane.

Injecting spin currents into antiferromagnets and realizing efficient spin-orbit-torque switching represents a challenging topic. Because of the diminishing magnetic susceptibility, current-induced antiferromagnetic dynamics remain poorly characterized, complicated by spurious effects. Here, by growing a thin film antiferromagnet, α-Fe_{2}O_{3}, along its nonbasal plane orientation, we realize a configuration where the spin-orbit torque from an injected spin current can unambiguously rotate and switch the Néel vector within the tilted easy plane, with an efficiency comparable to that of classical ferrimagnetic insulators. Our study introduces a new platform for quantitatively characterizing switching and oscillation dynamics in antiferromagnets.

Research of Electrophysical Properties of Thin Gate Dielectrics Obtained by Rapid Thermal Processing Method

Researches of the electrophysical characteristics of gate dielectrics obtained by the rapid thermal processing (RTP) method by two-stage and three-stage processes have been carried out. Each photonic processing (stage) was carried out for 12 s at a constant power of halogen lamps and heating the wafers to a maximum temperature of 1250 °C. The first two stages of the process were carried out in an oxygen atmosphere, the third - in nitrogen or a forming gas. It was found that for dielectrics obtained by the process with final processing in a nitrogen atmosphere, the absolute value of the voltage of flat zones is 0.42 V less, than for insulators, formed by a two-stage process. This is the consequence of the elimination of a significant part of the defects, responsible for the presence of Coulomb centers in the dielectric layer. Carrying out photonic processing in anitrogen atmosphere at high temperatures of procedures for proceeding of the restructuring of the structure of the dielectric layer. For insulators obtained by a three-stage process with final processing in N2, an increase in dielectric strength and breakdown voltage by 1 V and 3.3 MV/cm, respectively, is observed in comparison with dielectrics, obtained by a two-stage process. An increase in dielectric strength indicates relaxation of elastic stresses of deformed bonds and compensation for dangling bonds both in the dielectric and at its interface with Si during high-temperature photonic treatment. Passivation by nitrogen atoms of deformations at the dielectric/semiconductor interface will also have a positive effect on the strength of the insulator.

Optimizing the topological properties of semiconductor-ferromagnet-superconductor heterostructures

We study the electronic properties of a planar semiconductor-superconductor heterostructure, in which a thin ferromagnetic insulator layer lies in between and acts as a spin filtering barrier. We find that in such a system one can simultaneously enhance the strengths of all the three important induced physical quantities, i.e., Rashba spin-orbit coupling, exchange coupling, and superconducting pairing potential, for the hybrid mode by external gating. Our results show the specific advantage of this stacked device geometry compared to conventional devices. We further discuss how to optimize geometrical parameters for the heterostructure and complement our numerical simulations with analytic calculations.

Giant magnetochiral anisotropy from quantum-confined surface states of topological insulator nanowires

Wireless technology relies on the conversion of alternating electromagnetic fields into direct currents, a process known as rectification. Although rectifiers are normally based on semiconductor diodes, quantum mechanical non-reciprocal transport effects that enable a highly controllable rectification were recently discovered1–9. One such effect is magnetochiral anisotropy (MCA)6–9, in which the resistance of a material or a device depends on both the direction of the current flow and an applied magnetic field. However, the size of rectification possible due to MCA is usually extremely small because MCA relies on inversion symmetry breaking that leads to the manifestation of spin–orbit coupling, which is a relativistic effect6–8. In typical materials, the rectification coefficient γ due to MCA is usually ∣γ∣ ≲ 1 A−1 T−1 (refs. 8–12) and the maximum values reported so far are ∣γ∣ ≈ 100 A−1 T−1 in carbon nanotubes13 and ZrTe5 (ref. 14). Here, to overcome this limitation, we artificially break the inversion symmetry via an applied gate voltage in thin topological insulator (TI) nanowire heterostructures and theoretically predict that such a symmetry breaking can lead to a giant MCA effect. Our prediction is confirmed via experiments on thin bulk-insulating (Bi1−xSbx)2Te3 (BST) TI nanowires, in which we observe an MCA consistent with theory and ∣γ∣ ≈ 100,000 A−1 T−1, a very large MCA rectification coefficient in a normal conductor.

Scalable Reflective Plasmonic Structural Colors from Nanoparticles and Cavity Resonances – the Cyan‐Magenta‐Yellow Approach

AbstractPlasmonic metasurfaces for color generation are emerging as important components for next generation display devices. Fabricating bright plasmonic colors economically and via easily scalable methods, however, remains difficult. Here, the authors demonstrate an efficient and scalable strategy based on colloidal lithography to fabricate silver‐based reflective metal–insulator–nanodisk plasmonic cavities that provide a cyan‐magenta‐yellow (CMY) color palette with high relative luminance. With the same basic structure, they exploit different mechanisms to efficiently produce a complete subtractive color palette. Finite‐difference time‐domain simulations reveal that these mechanisms include gap surface plasmon modes for thin insulators and hybridized modes between disk plasmons and Fabry–Pérot modes for thicker systems. To produce yellow hues, they take advantage of higher‐energy gap surface plasmon modes to allow resonance dips in the blue spectral region for comparably large nanodisks, thereby circumventing difficult fabrication of nanodisks less than 80 nm. It is anticipated that incorporation of these strategies can reduce fabrication constraints, produce bright saturated colors, and expedite large‐scale production.

Geometric control of topological dynamics in a singing saw

The common handsaw can be converted into a bowed musical instrument capable of producing exquisitely sustained notes when its blade is appropriately bent. Acoustic modes localized at an inflection point are known to underlie the saw’s sonorous quality, yet the origin of localization has remained mysterious. Here we uncover a topological basis for the existence of localized modes that relies on and is protected by spatial curvature. By combining experimental demonstrations, theory, and computation, we show how spatial variations in blade curvature control the localization of these trapped states, allowing the saw to function as a geometrically tunable high-quality oscillator. Our work establishes an unexpected connection between the dynamics of thin shells and topological insulators and offers a robust principle to design high-quality resonators across scales, from macroscopic instruments to nanoscale devices, simply through geometry.

Miniaturized Four-Arm Log-Periodic Toothed Antenna With Wide Bandwidth

An improved method of wideband performance is demonstrated by being applied to a miniaturized four-arm log-periodic toothed antenna with an integrated balun. The required minimum length of the integrated balun is reduced through the input impedance reduction structure on thin dielectrics with a low relative dielectric constant. In addition, destructive currents arising from the combination of the antenna structure and miniaturization structure are solved by modeling them as an equivalent circuit structure from an impedance perspective. The proposed antenna represents a voltage standing wave ratio of less than 2:1 in the 1.25&#x2013;18 GHz bandwidth range and has a realization gain of more than 2 dBi in the overall operating band with a diameter of 0.325 <inline-formula><tex-math notation="LaTeX">$\mathbf{\lambda}_{\mathbf {L}}$</tex-math></inline-formula>.

Transport properties of optically thin solid dielectrics from frequency correlations of randomly scattered light: publisher's note.

This publisher's note contains a correction to Opt. Lett.47, 1439 (2022)10.1364/OL.449084.

Transport properties of optically thin solid dielectrics from frequency correlations of randomly scattered light.

Frequency-dependent intensity correlation function measurements can be employed to determine the optical turbidity of solid disordered dielectrics. Here we demonstrate a speckle frequency correlation experiment with a focused beam and using an area detector. We show how to apply frequency correlation measurements to optically thin solid samples with the aim of determining the light diffusion coefficient and transport mean free path ℓ*. To give a practical example, we extract the optical transport mean free path of PTFE (Teflon) slabs, with a thickness of L = 0.4-3.5 mm, covering optical densities L/ℓ* ∼ 4-15.

Vertical oxide thin-film transistor with interfacial oxidation

A vertical oxide thin-film transistor was developed with interfacial oxidation for low voltage operation. The gate metal was used as a spacer for the definition of the transistor’s channel as well as the gate electrode. After definition of the vertical side wall, an IGZO (In-Ga-Zn Oxide) layer was deposited, followed by the interfacial oxidation to form a thin gate insulator. Ta was used for the gate material due to the low Gibbs free energy and high dielectric constant of tantalum oxide. A 15 nm tantalum oxide layer was obtained by the interfacial oxidation of Ta at 400 °C under oxygen atmosphere. The thin gate oxide made it possible to operate the transistor under 1 V. The low operation voltage enables low power consumption, which is essential for mobile application.

SPICE Implementation of the Dynamic Memdiode Model for Bipolar Resistive Switching Devices.

This paper reports the fundamentals and the SPICE implementation of the Dynamic Memdiode Model (DMM) for the conduction characteristics of bipolar-type resistive switching (RS) devices. Following Prof. Chua’s memristive devices theory, the memdiode model comprises two equations, one for the electron transport based on a heuristic extension of the quantum point-contact model for filamentary conduction in thin dielectrics and a second equation for the internal memory state related to the reversible displacement of atomic species within the oxide film. The DMM represents a breakthrough with respect to the previous Quasi-static Memdiode Model (QMM) since it describes the memory state of the device as a balance equation incorporating both the snapback and snapforward effects, features of utmost importance for the accurate and realistic simulation of the RS phenomenon. The DMM allows simple setting of the initial memory condition as well as decoupled modeling of the set and reset transitions. The model equations are implemented in the LTSpice simulator using an equivalent circuital approach with behavioral components and sources. The practical details of the model implementation and its modes of use are also discussed.

Modified Ramped Current Stress Technique for Monitoring Thin Dielectrics Reliability and Charge Degradation

Herein, a novel technique to monitor the quality and reliability of thin nano‐scale dielectric films is suggested. The method is based on the modification of the current stress technique (J‐Ramp) described in the corresponding JEDEC standard. The proposed technique, in addition to the J‐ramp tests, allows monitoring a change of charge state of the gate dielectric during all the tests. To implement this, in the suggested method before each transition to a higher current level, the current level is switched to the injection mode by a measurement current level and the change of voltage across the metal–insulator–semiconductor (MIS) structure is measured. A density of the measurement current level is chosen based on the condition that under this current level, a considerable charge degradation of the dielectric should not be observed, and the switches to the measurement current level should not considerably influence the studied sample. In addition to the monitoring of the charge injected until the dielectric breakdown, the proposed method allows to monitor the value of the injected charge at which the unacceptable degradation of MIS device characteristics takes place and, accordingly, to estimate the reliability of the dielectric film based on statistical measurements of these values.

Dark electron tunneling current in metal–insulator–metal structures: modeling, fabrication, and measurement

Metal–insulator–metal (MIM) structures have been proposed for infrared photodetectors, optical rectennas, and alternative choices to conventional solar cells. Generally, if two dissimilar electrodes are separated by a sufficiently thin insulator, electrons can travel through the insulating gap region due to the quantum tunneling effect. This tunneling through the insulating gap can be driven by an electromagnetic field or an external bias voltage. In our work, we incorporate the contributions of the Poole–Frenkel (PF) effect on the energy barrier of the MIM junction and the effect of Coulomb interaction between the electron charge and its virtual image charges. Using this modified PF-Coulombic barrier, we perform quantum calculations for electron tunneling using the transfer matrix method and Wentzel–Kramers–Brillouin approximations. This, along with the density of states, the Fermi occupation probability, and the quantum confinement effect is used to derive the dark current density for the MIM diode. To test the theory, MIM Au-TiO2-Ti diodes are designed and fabricated in-house using photolithography, along with electron beam evaporation and sputter depositions. The dark current–voltage (I − V) characteristics of the fabricated MIM photodiodes are measured and show good agreement with theoretical predictions.

Iron lamination and interlaminar insulation for high-frequency pulsed magnets.

In high-frequency pulsed magnets, such as kickers in particle accelerators, it is essential to reduce eddy currents that could be induced in the magnet core during excitation not to distort and attenuate the magnetic field pulse. A novel iron lamination scheme with additional interlaminar insulation is proposed for the magnet core of such pulsed magnets. A laminated steel sheet core is formed by alternately stacking thin steel and insulation sheets. For application to matched kicker magnets for accelerators, test magnets with the new and conventional iron lamination were designed, assembled, and extensively evaluated. The pulsed magnetic field waveforms of two test magnets with the new lamination successfully matched to below 0.1% over the entire pulse duration, which was significantly better than those with the conventional lamination. Among the applications of the developed high-frequency pulsed magnets, beam injection kickers for the coming next generation light sources and future colliders, where suppression of the transient stored-beam oscillation during beam injection is crucial, are considered to be promising.

Surface Plasmon Resonance of Two-Dimensional Gold Colloidal Crystals Formed on Gold Plates.

The free electrons inside precious metals such as Au vibrate when the surface of the metal is irradiated with an electromagnetic wave of an appropriate frequency. This oscillation is referred to as surface plasmon resonance (SPR), and the resonance frequency varies with permittivity of the medium around the metal. SPR sensors are widely applied in the fields of bioscience and pharmaceutical sciences, including biosensing for drug discovery, biomarker screening, virus detection, and testing for food safety. Here, we fabricated a metal-insulator-metal (MIM) SPR sensor by constructing two-dimensional (2D) regular array of Au colloidal particles (2D colloidal crystals) on an insulator layer over a thin Au film coated on a glass substrate surface. The 2D crystals were fabricated by electrostatically adsorbing negatively charged three-dimensional crystals onto a positively charged thin insulator formed on Au film. The plasmon peaks/dips from the MIM structure were measured in aqueous solutions of ethylene glycol (EG) at various concentrations. Multiple plasmon peaks/dips were observed due to the localized SPR (LSPR) of the Au particles and the Fano resonance between the Au particles and thin film. The plasmon peaks/dips shifted to higher wavelengths on increasing EG concentrations due to an increase in the refractive index of the media. The observed peak/dip shift was approximately twice that of LSPR from an isolated Au particle. We expect the present MIM substrate will be useful as a highly sensitive sensor in the pharmaceutical field.

Charging properties of thin gate dielectrics, obtained by the method of rapid thermal processing

The charge properties of thin dielectrics, obtained by rapid thermal processing (RTP), and their interfaces with silicon for MOS transistors are investigated. The production of insulator layers was carried out by a two- or three-stage RTP with photon processing regimes similar for each stage (duration – 12 s, maximum temperature – 1250 °C). After the third stage of RTP in a nitrogen atmosphere of the gate oxides, obtained by a two-stage process in oxygen atmosphere, the defects responsible for local charge centers are partially eliminated. There is also an increase in the relative value of the surface potential by an average of 100 relative units. The elimination of defects is a consequence of the rearrangement of the structure of the dielectric, its interface with silicon, and the diffusion of oxygen and silicon atoms along the interface of the insulator layer. For samples obtained by a two-stage RTP in an oxygen atmosphere and subjected to the third stage of processing in a forming gas, there is an almost complete elimination of local charge centers and an increase in the relative value of the surface potential by an average of 300 relative units. In this case, in addition to the processes occurring during the treatment of SiO2 by the RTP method in an nitrogen atmosphere, the liquidation of charge centers is a consequence of the passivation of defects by hydrogen atoms.

Impact of interlayer insulator formation methods on HfOx ferroelectricity in the metal–ferroelectric–insulator–semiconductor stack

It has been reported that the HfOx-based metal–ferroelectric–insulator–semiconductor (MFIS) stack is one of the most feasible structures for memory applications in ferroelectric devices. In addition, in MFIS stacks, the formation of a high-quality thin insulator is considered to be a crucial process, because it determines the device performance and reliability. In this study, the effects of different SiO2 thin interfacial layers (ILs) formed by chemical oxidation and atomic layer deposition (ALD) on the ferroelectricity of HfOx were investigated in MFIS stacks. Notably, the IL formation method affected the crystallization temperature of HfOx ferroelectricity. In particular, the chemical oxide IL sample was sufficiently crystallized only at an RTA temperature greater than 800 °C, whereas the ALD oxide IL sample began to undergo a complete ferroelectric phase transition from a low temperature (600 °C). The x-ray analysis verified that the IL formation method affected the initial film state of the HfOx layer by modulating the Hf-O bonding states, resulting in a different temperature dependence for ferroelectricity formation during the subsequent crystallization annealing stage. Consequently, it was confirmed that stable polarization (2Pr &amp;gt; 30 μC/cm2) could be obtained over a wide temperature range (600–800 °C) through IL material engineering; this could facilitate the integration of HfOx-based ferroelectric devices in terms of the heat budget and the application of ferroelectric devices as commercial devices.

Исследование трибоэлектрических зарядов в тонких диэлектрических и полупроводниковых пленках методами сканирующей зондовой микроскопии

Abstract SPM studies of triboelectric charges on thin films of high-k dielectrics LaScO3, semiconductor ”flakes“ MoSe2, and ferroelectric PZT films have been carried out. It is shown that the value of the accumulated triboelectric charge in these films depends on their thickness. The strongest effect is observed in the LaScO3 film 6 nm thick and the PZT film 100 nm thick. The dependence of the value of the measured triboelectric potential on the loading force and the material of the probe was also experimentally found.

Quench Transient Simulation in a Self-Protected Magnet with a 3D Finite-Difference Scheme

The quench process in a superconducting magnet is inherently transient and three-dimensional (3D). In many cases, such as magnets protected by active protection systems, this transient can be accurately simulated with a two-dimensional model. However, a more complex 3D model is required in the case of a self-protected magnet. Simulations are particularly challenging due to physical and geometrical features, such as highly non-linear material properties, sudden appearance of localized heat generation, non-isotropic conductors, and relatively thin insulation layers. In this work, it is shown how the quench and heat diffusion in 3D geometry can be accurately yet rapidly simulated using the finite-difference method. The coupled electro-thermal problem is solved with a semi-implicit Euler method. This 3D approach is included as a new feature in the STEAM-LEDET quench simulation software. As a study case, a simulation of the transient following a quench occurring in one of the self-protected LHC magnets is presented. Simulation results are found in excellent agreement with experimental results. The influence of 2D and 3D geometry, inter-filament coupling loss, and quench location on the simulated transient is discussed.